Evaluation of Adhesion Performance of Electrodeposited Nickel Coatings on Copper and Molybdenum Substrates Using Different Techniques

For analysis of adhesion performance, the composite structures consisting of electrodeposited (ED) nickel coatings on copper and molybdenum substrates were prepared. Optimal electrodeposition process parameters, significant for adhesion testing, were determined. With the experimentally determined deposition rate for a current density of $35 ~\text{mA} / \text{cm}^{2}, 0.7 \mu ~\mathrm{m} / \text{min}$, the deposition time was calculated for coating thicknesses of $\mathbf{5, 1 0}$ and $20 \mu ~\mathrm{m}$. The adhesion performance of the “hard coating on a soft substrate” composite systems was investigated using three types of adhesion testing: a bidirectional bending test, a crosshatching method, and a Vickers microindentation method. The morphology of the surfaces of substrates and coatings before and after the adhesion testing was examined using a stereomicroscope and a metallurgical microscope. The adhesion strength of nickel coatings on molybdenum substrate was poor and decreased with increasing coating thickness, but on copper substrates, adhesion strength was excellent for all the coating thicknesses. Different adhesion tests gave consistent results.